Acoustical panel



Jan. 26, 1965 w. A. JACK ETAL 3,167,151

ACOUSTICAL PANEL Filed June 7, 1962 H V; r- Pi 3. 26 /47 5", 1

INVENTOR. WILLIAM A- (TA K Gaono: W. Cousmm'm ATTORNEY United StatesPatent 3,167,151 ACOUSTICAL PANEL William A. Jack, Hampton, and GeorgeW. Constantin,

Lebanon, N.J., assignors to Johns-Manville Corporation, New York, N.Y.,a corporation of New York Filed June 7, 1962, Ser. No. 200,786 1 Claim.(Cl. 18133) This invention relates to acoustical panels; morespecifically, it relates to a method for forming perforations in asurface of an acoustical panel to increase the esthetic effect and thesound absorbing coefficient or sound absorbing etficiency of such apanel.

This application is a continuation-in-part of US. patent applicationSerial No. 780,836, filed December 16, 1958, now abandoned.

It is well known in the art of acoustical panels to form a plurality ofperforations in one of the surfaces of a panel, Which perforationsextend from the surface into the body portion thereof. Such perforationsopen up the body portion of the panel, which is adapted to beencountered by sound waves, thereby greatly increasing the panels soundabsorbing efficiency or sound absorbing coelfic-ient.

The conventional methods of forming such perforations are either todrill the surface of such a panel or to punch the panel surface with asharply pointed punch. The perforations are formed either in anirregular pattern or in a regular series of columns and rows.

A novel method of producing such perforations, and the novel panelproduced thereby is disclosed in the copending application of William A.lack and Samuel G. Nelson, Serial No. 87,988, filed February 7, 1961,now abandoned and assigned to the assignee of the present invention.This copending application discloses a methed for forming perforationshaving cavities or marked delaminated areas circumambient suchperforations by the use of blunt punches. The present application is animprovement in the formation of such perforations in a surface of anacoustical panel whereby the surface appearance of the perforation isgreatly improved and the sizes of the perforations may be increasedwhile maintaining the panels surface integrity.

An object of this invention is to provide a method of increasing thesize of perforations in certain types of acoustical panels using astepped punch, preferably one having a blunt end, which perforationswere, heretofore, difficult to obtain because of the destruction of thesurface integrity of the panels during the forming of the perforations.

Another object of this invention is to provide a method of forming neatsurface perforations in an acoustical panel while, at the same timeproducing an acoustical panel having a relatively high coefficient ofsound absorption.

In brief, this invention comprises a novel method of formingperforations in an acoustical panel, and the novel acoustical panelformed thereby. According to thi method, an acoustical panel surface,adapted to be encountered by sound waves, is perforated by a steppedpunch, preferably one with a blunt, pilot end, or a plurality of suchpunches, to produce a perforation, or a plurality of such perforations,from the surface of the panel into the body portion thereof. Each suchperforation formed by the stepped punch in the surface of the acousticalpanel is of such a nature that it is of approximately the samecross-sectional area at the surface of the panel as the cross-sectionalarea of the final diameter of the working portion of the punch. Suchperforations formed by the stepped punch present a neater appearanceatthe panel surface than perforations formed by straight-walled bluntpunches of the same diameter as the ultimate working diameter of thestepped punch. Also surprisingly, the perforations are also smaller incros-s sectional area at the panel surface than the crosssectional areasof the perforations formed by a blunt punch without such stepped portionand having the same diameter as the ultimate working diameter of thestepped punch of the present invention. 7

These and other objects will be readily apparent from the precedingbrief description and the following more detailed description and theattached drawings wherein:

FIG. 1 is a perspective view of a perforated acoustical panel having itsperforations formed by a straight, cylindrical, blunt end punch;

FIG. 2 is an enlarged cross-sectional view taken along lines 2-2 of FIG.1;

FIG. 3 is a perspective view of an acoustical panel having itperforations formed according to the present invention;

FIG. 4 is an enlarged cross-sectional view taken along lines 4--4 ofFIG. 3;

FIG. 5 is a partial view, in elevation, of a punch used to form theperforations evidenced by FIGS. 1 and 2; and,

FIG. 6 is a partial view, in elevation, of the punch of the presentinvention used in forming the perforations of the panel of FIGS. 3 and4.

In the aforesaid copending application of William A. Jack and Samuel G.Nelson, Serial No. 87,988, filed February 7, 1961, a method has beendescribed wherein a unique type of perforation is formed in a fibrousacoustical panel. A panel, formed with these perforations, is shown inFIG. 1 and, as depicted, has a plurality of irregular perforations 3, ina random pattern, extending from a surface 2 of the fibrous panel 1 intothe body portion thereof. If a blunt punch, circular in crossseotion, isused to form these perforations, as, for example, the punch 6 having aplunt end 7 shown in FIG. 5, the cross-sectional area of eachperforation at the surface 2 of the panel 1 is quite irregular and ismuch larger in cross-sectional area at the panel surface than thecrossectional area of the punch used to form such perforations. If sucha punch 6 is circular in crosssection, the perforations 3 at the visiblesurface are not, relatively speaking, also circular. The edges of theperforations at the surface of the panel 1 are quite ragged following nopreconceived pattern. The enlargement of the aperture and ragged edgeeffect results from the fibrous nature of the panel and from the mannerthat the fibers are interlaced or intertwined. The blunt punch enteringthe surface of the panel does not sharply shear the main body of fibersadjacent the punch; rather, there is a tendency towards pulling away ofthe fibers and the creation of compressing shives or clusters of fibers.Some shearing of the fibers, of course, occurs. However, the net resultof this punching action is to produce an aperture or perforation havinga cross-section at the panel surface noticeably greater in area than thecross-sectional area of the punch, and, because of the pulling away ofthe fibers, the perforation edges are not cleanly defined but have asomewhat ragged-edge appearance. Within the body portion of the panel,each perforation 3 (FIG. 2) also has a delaminated area or cavity 4circumambient each such perforation and a ragged wall area 5 forming thewall surface of each perforation.

The preferred embodiment of this invention comprises a panel 11, similarin nature to the panel 1 described briefly above and in the aforesaidcopending application of William A. lack and Samuel G. Nelson, and whichpanel has a surface appearance somewhat similar to that of panel 1, thatis to say, a plurality of perforations 13 extend from a surface 12 ofthe panel 11 into the body a portion thereof. However, each suchperforation 13 is more circular in cross-section and presents a muchneater appearance than the ragged-edge perforations 3 of the panel 1.Referring to FIG. 4, at times the perforations 13 have circumarnbientthereto pairs of marked delaminated areas or cavities 14, 15. The firstis adjacent the surface 12 of each such panel and the second adjacentthe bottom of the perforation. The wall surface area 26 is formed ofragged edges, similar in nature to the Wall surface area 5 of theacoustical panel 1. This double cavity effect, however, does not occurat all times, even in the same panel. Why it does or does not occur isdiiiicult to determine, since the diameters of the punches are verysmall. The effect is not produced with rather shallow punching or withrelatively thin panels (which results in a situation similar to shallowpunching);

The perforations 13 in the surface 12 are formed :by pressing a steppedpunch 16 (FIG. 6) or a plurality of such punches, from said surface intothe body portion of the sheet or panel. The punch is of the stepped typeand has a small diameter, cylindrical portion or pilot 18, preferablywith a blunt end 26, and a larger diameter portion 17 extending from theopposite end. A shoulder or step 19 is formed in the bottom of acylindrical portion 17 interconnecting the cylindrical walls of the twocylindrical portions. For the purpose of comparison and furtherdescription, the diameter D of the larger diameter section or theultimateworking portion 17 has been made equal to the diameter D ofpunch 6 of FIG. 5.

In forming the perforations in an acoustical panel, the end 2% of punch16 is pressed into the surface 12 thereby forming an initial perforationaccording to the diameter d of the smaller section 18. As the punch 16progresses through the panel, a delaminated area or cavity 14- (FIG. 4)is formed in the acoustical panel created by the tearing away of thefibers circumadjacent the punch. As such progression continues, theresistance to further travel of the punch increases to a maximum until abreak-through occurs and a second delaminated area 15 'is commenced tobe created by further movement of the punch. This break-through is verynoticeable duringthe puncturing of the panel, and is marked [by a suddenyielding of the panel to the action of the punch. This yielding isbelieved to result from the fact that after the break-through, the punchcontinues perforating as if a new panel were encouitered, that is tosay, the action and feel of continued perforation is approximately thesame as perforating initially from the surface 12. The cavity 15 isenlarged until the rear side of the panel is approached or until thepanel resistance mounts such that further penetration of the step punch16 into the body portion of the panel ecomes difiicult, at which timesthe aperture 13 is complete, and the punch is withdrawn. During thetravel of the stepped punch 16 into the body portion of the panel, thestepped area 19 mates with the surface of the panel 12 and commences toform a surface perforation 13 according to the diameter D of the largerdiameter section 17. However, a cavity 14 lies subjacent the surface 12and the stepped area 19, so that resistance to penetration of the lar erdiameter section or ultimate working section 17 is very slight.Consequently, the hole is, in effect, dressed, and the formed hole oraperture closely follows the contour 'of the larger diameter section 17.On further travel of the stepped punch and approximately at the time thesecond cavity is being formed, the shoulder 19 engages the bottom of thefirst cavity 14 and forces the bottom of this cavity further away fromthe surface 12 and tends to enlarge the cavity. Since, at this time, thesecond cavity 15 is also being 7 formed by the lower end 18 of the punch16, the backing support. for'the first cavity 14 is, in part, removedthereby permitting such enlargement of the first cavity. Upon removal ofthe punch, and after the panel has been mounted to form a wall surface,the interior areas 14 and 15 are not visible, and the ultimateperforation 13 has an appearance similar to a drilled or pierce punchedperforation or opening having a cross-sectional area equal to thecross-sectional area of the larger section 17 of the step punch 16.

As previously noted, the double cavity effect is not always produced.With some panels, the double cavity effect is produced much less oftenthan a modified single cavity effect (FIG. 2). Moreover, the doublecavity efiect is difficult 'to obtain when the perforations arepurposely made'rather shallow due to the limitations of the material.For example, if the thickness of the panel is /2 inch, or thereabouts,the stepped punch perforation is made deep, but the depth of penetrationi not very great. With this depth, a perforation made in thicker boardswould be considered shallow. 'As a re suit, the double cavity effectis-difiicult to obtain in such thin, /2 inch thick panels. Nevertheless,the sound absorption :of the panels having perforations formed bystepped punches, even Where the double cavity effect is not apparentapproximates closely the sound absorption of the panels havingperforations formed by straightwalled punches. Why this is so is notclear, as it would appear that the sound absorption of the latter panelsshould be much greater, since the straight-Walled punch at its leadextremity is of much greater diameter than the extremity of the steppedpunch (with punches of the same ultimate working diameters). One wouldsupect that the holes formed would be larger, the cavities larger, and,resultantly, the sound absorption greater. Yet, paradoxically, theperforations formed by stepped punches show approximately the same soundabsorbing characteristics. One of the factors which might tend toequalize sound absorption is the fact that the bottoms of theperforations formed by stepped punches are believed to have lesstendency to spring back than the bottoms of the perforations formed bystraight-walled, blunt punches. The bottoms of the perforations, formedeither by straight-walled or step punches, are compressed to somedegree. In the perforation of FIG. 2, for example, the bottom of theperforation has a tendency to spring back or to relieve the compression,which may in turn, tend to cause the cavity 4 to decrease in the degreeof openness. In the perforation formed by a stepped punch, it appearsthat the pilot end of the punch tends to pin down or tack the materialat the bottom of the perforation. Such action tends to reduce the amountof spring back effect, thereby tending to maintain the size of thecavity formed.

To create a commercially acceptable panel, ordinarily a small diameteredblunt punch must be used, since, with the larger diametered punches,almost complete destruction of the surface and interior of the paneloccurs. Thus with the larger diametered punches of FIG. 5, it isoftentimes diihcult to maintain the integrity of the panel. 7

The maximum size of straight punch for the creation of a commerciallyacceptable panel will vary with the type of panel used, i.e., organic orinorganic, the density of the panel, the thickness, the method ofmanufacture, the standards of manufacture, the esthetic effects desiredto be produced, etc. With the use of the preferred embodiment of thepresent invention, these various factors do not present such an imposingobstacle, as the pilot diameter d is appreciably less than the diameterD of the'final working portion 17 of the punch 16, and, ordinarily, wellwithin the range of satisfactory smaller diameter sizes of punhces.While the perforations 3 of FIG. 1 are somewhat exaggerated in sizerelative to the perforations 13 of FIG. 3, there is a marked differencebetween these perforations and the perforations 13 formed according tothe preferred embodiment of the present invention. As note-:1, theperforations 13 have a general appearance as if they were formed bysharply pointed punches or by drills. In contrast to this, theperforations 3 have a surface cross-sectional area formed of raggededges and, quite noticeably, are much larger in average diameter or inaverage surface cross-sectional area than the perforations 13.

Although circular punches 6 and 16 and circular perforations 3 :and 13have been described herein, it is to be understood that the particularcross-section of the punches and the cross-section of the perforationsformed may be altered to fit particular design requirements.

The particular stepped punch used had a diameter D=.08 and a diameterd=.055", or roughly the ratio of the two diameters was 0.7. Obviously,these ratios may be altered to fit particular requirements and toproduce various acoustical design or esthetic effects. Likewise, theseratios may be altered to fit the particular density or construction ofthe acoustical panels. The height of the lesser diameter section 18 washowever, this height also may be altered depending upon the density,thickness, and the particular construction of the acoustical panels.

One of the striking advantages of the method of the prefen'ed embodimentof the present invention in forming apertures having delaminated areasis that blunt punches of greater diameter may be used, which, of course,will produce relatively large apertures in a panel surface. If the punchof FIG. 5 were to be enlarged greatly, say to and if the panel to beperforated were of the wood fiber type, such a blunt punch would producea tearing of the fibers to such an extent that a large area adjacent thepunch would be completely broken up. Even if such a large aperture wereto be formed, such a large delamination would be produced that theportion above the delamination adjacent the panel surface would bereadily crushed or depressed upon application of the slightest pressure.This phenomenon does not occur with the stepped punches. The ultimateworking diameter D of the upper section 17 may be approximately but thedelamination formed by diameter a of the lower sec tion 18, then will,in all probabilit be considerably less than The appropriate pilotdiameter would be selected which would produce the desired cavity eifectwithout the destruction of the interior portion of the panelaforementioned and which would present an aperture for the largerdiametered section suitable for dressing. With a ratio of 0.5 or 0.7,the range of pilot diameters would roughly be between 0.09 and 0.13,which diameters are considered to be more on the smaller side than onthe larger side.

The particular types of panels to which this present invention isapplicable have been described in the aforementioned copendingapplication. Briefly, such panels generally are of the organic orcellulosic type, as, for example, panels made of wood fiber, vegetablefiber, bag-asse, etc, or fibrous type panels, both of the inorganic andorganic, made according to the wet process method of forming suchpanels. The wet process is well-known in the art and follows generally apapermaking process. Basically, the process comprises the mixing offibers, as, for example, wood fibers, with a suitable binder and water.The solids content in this mixture is very low, being about 23%. Thesolids are picked up or deposited on a vacuurn machine and transferredtherefrom to a conveyor belt. The conveyed material is pressed into adesired thickness and cut into the desired shapes. Ordinarily, thematerial is also cooked or baked to evaporate the residue moisturecontained therein.

The present invention is particularly adapted to the organic orcellulosic class of acoustical panels, exemplified by wood fiber boards,of densities between 820 lb./ cu. ft., as such panels have fibers formedtherein which are tough, not readily friable, and markedly resistant tothe pressing action of straight, blunt punches (PEG. 5).

Having thus described our invention in rather full detail, it will beunderstood that the details are given for the purpose of illustration,not restriction, and that variations within the spirit of the inventionare intended to be included within the scope of the appended claim.

What we claim is:

A method of opening up the surface and body of a fibrous acousticalpanel of the water-laid type, said surface being fibrous and relativelyplanar, comprising the steps of pressing a stepped punch, having a pilotblunt portion and at least one shoulder along the length thereof, intosaid surface to a depth sufficient to create a delaminated area withinthe body portion of the panel, and continuing pressure on the punchuntil the larger diametered portion thereof, includin the shoulder,enters the surface of the panel.

References Cited in the file of this patent UNITED STATES PATENTS295,227 Briggs et al Mar. 18, 1884 1,554,180 Trader Sept. 15, 19251,837,451 Lee Dec. 22, 1931 2,642,359 Scott June 16, 1953 2,667,925Dalphone Feb. 2, 1954 2,668,123 Copeland Feb. 2, 1954 2,968,327 MarinerJan. 17, 1961 3,013,626 Brown et a1 Dec. 19, 1961 3,017,947 Eckert Jan.23, 1962 FOREIGN PATENTS 67,328 Denmark July 19, 1948

